This invention relates to internal reforming fuel cell systems and, in particular, to internal reforming fuel cell systems which utilize methane as the fuel supply.
It is known that internal reforming fuel cells, such as, for example, internal reforming molten carbonate fuel cells, have high energy conversion efficiency when the fuel to the cells is methane. It is also known that in the production of methane by a gasifier, cold-gas efficiency is optimum when methane production is optimized.
These known factors have led to proposals for utilizing a methane producing gasifier in combination with an internal reforming fuel cell as a way of achieving an overall power plant with high thermal efficiency. Furthermore, studies have shown that such a power plant could provide a high overall coal to electrical energy conversion efficiency.
Typical methane producing gasifiers usually operate at lower temperatures and higher pressures than non-methane producing gasifiers. However, methane producing gasifiers require, in addition to their feedstock, quantities of hydrogen and steam for their endothermic hydro-gasification reactions. In presently proposed systems, this hydrogen is developed from the gasifier output, upstream of the fuel cell. While this offers a viable way of generating the required hydrogen, other more efficient ways are being sought.
It is, therefore, a primary object of the present invention to provide an internal reforming fuel cell system in which a methane gasifier is used in a way which better promotes the overall efficiency of system.
It is a further object of the present invention to provide an internal reforming fuel cell system in which improved efficiency of the overall system is achieved through the manner of developing the hydrogen for the methane gasifier of the system.